In recent years, various plastic materials having optical characteristics such as high transparency have been used for lenses such as lenses for eyeglasses, f·θ lenses and pick up lenses, prisms, optical fibers, disk substrates for an optical recording medium or a magneto-optical recording medium, and constituents of a liquid crystal displays. It is important for plastic materials, particularly, those used as a material for a constituent of optical systems in a liquid crystal display provided with a carrying plate, a polarizing plate, a substrate of liquid crystal cells, a light diffusion plate and a condensing film, to be transparent as well as superior in their properties to polarization and their heat resistance. However, plastic materials now used for a constituent of optical systems in an optical product are not sufficient in their properties to polarization. For example, a liquid crystal display comprising a part of a conventional plastic material as the optical systems frequently results in change in a display color tone depending upon variation of using circumstances such as a temperature variation and a humidity variation.